Landscape care tools, such as garden care tools, most traditionally have drive trains based upon rotation of a shaft, most typically a shaft from a motor and, in many cases, an additional tool shaft coupled to the motor shaft. And a variety of such tools incorporate straight-forward rotational movement at the output part of the tool which performs the output operations. For example, line trimmers for cutting vegetation typically have rotating heads carrying extended lengths of line to perform the cutting. And snow throwers, which pick up and throw aside snow, and air blowers, which blow aside leaves and other cut or fallen vegetation, typically incorporate an impeller which rotates in straight-forward fashion.
On the other hand, power hoes (or cultivators) based on the "back-and-forth" motion of hoeing tines, do not apply straight-forward rotation at their outputs. As indicated, they adopt a form of cyclical, reversing movement. Moulton, U.S. Pat. No. 4,351,396, issued Apr. 3, 1987, and to be reissued as Moulton et al., U.S. Reissue Pat. No. 33,238, on Jun. 26, 1990, and Motruk, U.S. Pat. No. 4,541,492, issued Sept. 17, 1985, are illustrative of such power hoes. The former emphasizes such apparatus incorporating a motor at the operating end of the tool and the latter emphasizes apparatus incorporating a motor at the other, user end of the tool. In both cases, the drive train incorporates a gear, an axle, and a crank-type arrangement with off-center throws, between the axle and the tines, to change straight rotational movement of a shaft to the back-and-forth movement of the tines. The assembly and operating instructions of HMC (Hawaiian Motor Co.), the assignee of the aforementioned patents, for apparatus including its Model 2370 cultivator and its Model 2371 and 3371 cultivator attachments are representative of up-to-date versions of the apparatus disclosed in such patents.
Another form of landscape care tool, more specifically, a form of vegetation-cutting apparatus, which does not embody straight-forward rotation at its operating output, is a tool known as a reciprocator, which incorporates a pair of generally round blades having teeth, which each turn in one direction and then in the opposite direction through an angle, directly out-of-phase with one another, so that the teeth on one blade and the teeth on the other blade cut vegetation between one another. The magazine Power Equipment Trade, January 1989, at pages 28-31, directed to the RedMax Reciprocator (Model SGC22DL), is illustrative. Specifically, in that apparatus, there is a pinion gear-ring gear arrangement, between the rotating tool shaft and a crank shaft, such crank shaft having a pair of off-center throws. Each throw then drives a link which turns a short shaft for one of the pair of blades. Because of the geometry, the short shaft for one of the blades is inside the short shaft for the other.
The present invention incorporates drive linkage which provides linear motion which is particularly beneficial in drive trains for cultivators and reciprocators which do not adopt straight-forward rotational movement at their operational outputs. The implementation is accomplished in a way which is an unusual blend of sophistication and simplicity. The invention is directed to a drive assembly incorporating such linkage, and to a tool incorporating such linkage, such as a tool for cutting vegetation through the rotational oscillation of circular-shaped cutting blades, or a tool for earth-working through the pendulum-like oscillation of hoeing tines. Specific linkage which converts rotational motion to the linear motion, and other specific linkage which provides a clutching function with damping with respect to linear motion, are also the subjects of the invention. Additionally, a form of blade assembly incorporating a pair of generally circular-shaped blades to cut vegetation through rotational oscillation, is provided.